It can be difficult to measure the increased porosity of the enamel by tooth decay, but this can be done using quantitative laser fluorescence (QLF). The method is based on visible light with a wavelength of 370 nm, addressing enamel. This produces an image consisting of red and green color tones and the dominant color of the enamel is green. Increased porosity of the enamel, resulting in a reduction of the auto-fluorescence and the loss (or gain) of the mineral can be quantified by means of a corresponding software.